Protists and Eukaryotic Diversity

• Protists are eukaryotes that aren't plants, animals, or fungi.
• Protist cells have membrane-enclosed organelles, enabling compartmentalization.
• Eukaryotic cells have a cytoskeleton, allowing them to change shape.
• Most eukaryotic lineages consist of protists.
• Protists exhibit greater eukaryotic diversity.
• Protists are mostly unicellular, with complex unicellular structures.
• Protists have all three basic types of sexual life cycles.
• Protists have diverse nutritional strategies like photoautotrophs, heterotrophs, and mixotrophs.
• Protistan diversity largely stems from endosymbiosis.
• Mitochondria evolved prior to plastids and originated from an alpha proteobacterium.
• Molecular analysis suggests that mitochondria and plastids originated once in life's history.

Plastid Evolution

• The evolution of mitochondria predates the rise of eukaryotes.
• Plastids came later, when heterotrophic eukaryotes engulfed photosynthetic cyanobacteria.
• Red and green algae evolved from the plastid-bearing ancestor.
• Plastids in red and green algae, like cyanobacteria, have two membranes.
• Transport proteins in these membranes are homologous to those in cyanobacteria.
• Red and green algae were ingested by heterotrophic eukaryotes during secondary endosymbiosis.
• Chlorarachniophytes evolved from a eukaryote engulfing green algae.
• The engulfed cell contains a vestigial nucleus called a nucleomorph.

Four Supergroups of Eukaryotes

• Eukaryotes are divided into four supergroups according to a current hypothesis.
• The four supergroups are Excavata, SAR, Archaeplastida, and Unikonta.

Excavates

• Excavata is characterized by its cytoskeleton.
• Some excavates feature an "excavated" feeding groove.
• Excavates include the monophyletic groups: diplomonads, parabasalids, and euglenozoans.
• Diplomonads have reduced mitochondria called mitosomes, and they lack electron transport chains.
• Diplomonads get energy from anaerobic pathways.
• Diplomonads posses two equal-sized nuclei and multiple flagella.
• Giardia intestinalis is a parasitic diplomonad.
• Parabasalids have reduced mitochondria called hydrogenosomes that generate energy anaerobically.
• They also lack plastids
• Hydrogen gas is released as a byproduct of anaerobic metabolism.
• Trichomonas vaginalis, a known parabasalid, is a sexually transmitted parasite.
• Euglenozoa is a diverse clade that includes predatory heterotrophs, photosynthetic autotrophs, mixotrophs, and parasites.
• A key feature of euglenozoans is a spiral or crystalline rod inside flagella.
• This clade includes kinetoplastids and euglenids.
• Kinetoplastids have a single mitochondrion with a kinetoplast (organized DNA mass).
• Trypanosomes are parasitic kinetoplastids with a single cell-surface protein that changes each generation.
• A "bait-and-switch" defense of trypanosomes prevents the host from developing immunity,
• Euglenids have one or two flagella emerging from a pocket on one end of the cell.
• Some euglenids are mixotrophs, switching between autotrophic and heterotrophic modes based on environmental conditions.

SAR Clade

• SAR is a monophyletic supergroup: stramenopiles, alveolates, and rhizarians.
• Diatoms are important photosynthetic stramenopiles.
• Many rhizarians are amoebas of type Globigerina.
• Stramenopiles include significant photosynthetic organisms.
• Stramenopiles usually possess a "hairy" flagellum paired with a "smooth" flagellum.
• Diatoms, oomycetes, and brown algae are stramenopiles.
• Diatoms are unicellular algae with unique two-part silicon dioxide walls.
• The diatom walls withstand 1.4 million kg/m² of pressure.
• After a bloom, dead diatoms decompose slowly on the ocean floor.
• Diatoms that decompose on the ocean floor can remain there for centuries.
• Diatom blooms are proposed to reduce levels of atmospheric CO2 when fertilized with essential nutrients.
• Brown algae are the largest, most complex multicellular algae.
• Brown color comes from carotenoids in the plastids.
• Most brown algae are marine and considered seaweeds.
• Brown algae present root-like holdfasts to anchor the alga, along with a stem-like stipe which supports the leaflike blades
• Brown algae can have gas-filled floats to keep photosynthetic structures near the surface.
• Brown algae lack true tissues and organs.
• Heteromorphic brown algae (like Laminaria) have different sporophytes and gametophytes.
• Isomorphic specifies that sporophytes and gametophytes look alike
• Oomycetes include water molds, white rusts, and downy mildews.
• Oomycete cell walls contain cellulose when compared to chitin.
• Oomycetes are related to plastid-bearing groups without plastids or photosynthetic ability.
• They acquire nutrients via parasitism or decomposition.
• Phytophthora infestans is an example of a parasite that is notorious for potato late blight.
• Alveolates possess of membrane-enclosed sacs (alveoli) found below the plasma membrane.
• Dinoflagellates, apicomplexans, and ciliates fall under the alveolates.
• Dinoflagellates are abundant in marine and freshwater phytoplankton.
• They have flagella that are housed in grooves of armor-like cellulose plates that surround the cell.
• Beating of the spiral flagella makes dinoflagellates spin through water.
• Apicomplexans are parasites of animals
• Apicomplexans spread as infectious cells called sporozoites.
• The apex of apicomplexans contains a complex of organelles which penetrate host cells and tissues.
• In the apicomplexan life cycle, most must have both sexual and asexual stages as well as at least two different hosts

Ciliates

• Ciliates utilize the cilia that move around and feed on bacteria or protists.
• The cilia covers cell or are in tufts.
• Ciliates have micronuclei and macronuclei.
• Their cells contain a copy of each.
• Macronuclei feature multiple copies of the genome.
• Micronuclei can be haploid and diploid
• Conjugation produces genetic variation through micronuclei exchange.
• Macronucleus dissolves and new one formed from micronuclei during binary fission.

Rhizarians

• Species of rhizarians fall under amoebas
• Amoebas are able to move and feed with pseudopodia, which are extensions of the cell surface.
• Rhizarian amoebas differ from other amoebas by their threadlike pseudopodia.
• Three clades under rhizarians are radiolarians, forams, and cercozoans.
• Radiolarians are delicate and asymmetrical, their internal skeletons are made completely out of silica.
• Pseudopodia features being reinforced by microtubules which radiate the central body.
• Prey are later engulfed into cytoplasm and pseudopodia, then moved into cell via cytoplasmic streaming
• Most radiolarians are from marine ecosystems
• Foraminiferans or forums are well known for calcium carbonate shells called tests
• The pseudopodia is found to extend through the pores, and is utilized in swimming, testing, and feeding.
• The fossils of forams are commonly found in the ocean and fresh water, but make up a generous amount of marine sediments.
• Fossilized tests are correlated with the age of sedimentary rocks from different geographical locations
• Cercozoans consist of amoeboid and flagellated protists that can feed thanks to their threadlike pseudopodia.
• The ecosystems they originate from are mostly marine, fresh water and soil ecosystems
• Most cercozoans consist of parasitic heterotrophs and predators

Archaeplastida

• Plastids sprung during heterotrophic protist acquisition from cyanobacterial endosymbiont.
• The ancient protist's photosynthetic descendants formed red and eventually green algae.
• Plants descended from the green algae.
• Archaeplastida supergroup are red algae, green algae and even plants.
• Red and green algae have cells that range from unicellular and colonial to the species with multicellularity,
• An exmaple of this will be Volvox, which would be a unicellular alga
• An accessory pigment called phycoerythrin masks the green of chlorophyll giving red algae its color
• Red Algae's colors range from reddish-green algae to very dark-red.
• Most are multicellular and the largest seaweed
• Their reproduction remains sexual and typically alternates by generations
• You usually see redgae growing in the depths of tropical oceans
• The greenness helps the green algae thanks to their green chloroplasts that help form strcutres and certain chemicals
• The green alage has a paraphyletic group of charophytes
• Most of their charophytes are algae which make them closely connected to most plants

Chlorophytes

• Most live in freshwater, but have a marine and land-like habitats as well.
• The species that fall inside of the many unicellulars can both free and symbiotic
• However, they have a habit to live inside intense climates and ultraviolet waves

Larger chlorophyte size and complexity

1. Creating colonies from their initial cells (Peditastrum)
2. True body multicellularity and cell diversification (olvox and ulva)
3. Nuclei division without dividing cytoplasm (Caulerpa).

• They come with complex cycles that include both secual and asexual.
• Almost all species have biflagellated gametes with cup-shaped chloroplasts.
• Alteration of generations has been seen in chlorophytes like ulva

Unikonta

• Unikonta supergroup is fungi, animal plus several other protists

• It also compromises of amoebozoans

• Amoevozaons are like lobes, or "tube shaped", instead od "threadlike"

• Included would be entaomoebas, slime molds, and tubulinids

• Its a group of diversified amoebozoans that feature tube shapes and lobed pseudopodia.

• Usually these are soil-like freshwater and marine environments

• Tubulinids are bacteria predators that prey on protisits, although some end up feeding on deitrtus

• Slimemolds are mycetozoans, or fungi that typically produce spores for fruiting.

• Results in the production of conversion that converts

• There are two slimemold types

1. Plasmodial Slimemold
2. Cellular Slimemold

Plasmodial slime molds

• Usually brightly colored as yellow or orange
• Form a plasomdium feeding mass
• The plasmodium can either come with either a "supercell" format or plasma membranes that have a diploid
• The plasmodium starts to fruit for reproduction at all cost to their enviroment

Cellular slimemolds

• This type of slime is formed by the cells that have multiceullular aggreagates
• Solitary cells help unite together to creat a slug-like feel to the slime mold

Entaomoebas

• Entaomeobas are in the same parasitical genus that all vertebrates and invertebrates are parasitized in
• Human host have a minimum of six or more species
• E.h causes ameobic dyseerty, the third ranked death due to eukaryotic parasites

Opisthokonts

• These are a mixed group of fungi, animals and some protists
• Protists thrive in most aquatic and humid ecosystems
• Protist tend to fulfill the role of the habitats their in.

Symbiotic Protists

• Benefit the hosts from having protist symnbiots
• Coral reefs often are nourised by dinolfagellates
• wood starts to come in contact with terminte guts, giving the protists to come in the form of wood digestion
• Some protozoa can parasitise the host
• Parasitism of Plasomidium leads to Malaria in humans
• The P.shumwayae that originates from dinoflagellates results is typically a parasite that feeds on shkin
• Phytophthora ramorum causes sudden oak death

Photosynthesis Protists

Many times portists are organisms that thrive off of the environment to convert CO2 to the organisms food source.

• Main protists are algae and prokaryotes that can also photosynthesize.
• The dependance on producers can either be directly or indirectly depend on them.
• They are also restricted by euteriants, althtough the population thrives of the nutrients it gets.
• A boom can have major ecosystemic effects thet result in an ecological collapse
• The increasing surface temp is related to growth and biomass declination.
• As that changes, phytoplankton relies on upwelling to keep it at a certain temp.

Explore the diverse world of protists, eukaryotes that aren't plants, animals, or fungi. This lesson delves into their cellular structure, nutritional strategies, and evolutionary history, including endosymbiosis and the origin of mitochondria and plastids. Understand how protists showcase the breadth of eukaryotic diversity and their unique life cycles.